Physical ScienceMotion and ForcesYear 3 Science

Pushes and pulls: what makes things move, stop and turn

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What this lesson covers

A push or a pull happens between two things
A still object only starts to move when it is pushed or pulled
Pushes and pulls can start, stop, speed up, slow down or turn a moving thing
A bigger push or pull makes a bigger change
Pushes and pulls can change a thing's shape
Shape, rough or smooth surfaces, air and water all change how things move

Key idea

Pushes and pulls

A push moves a thing away from you. A pull moves it towards you.
Kicking a ball is a push. Opening a drawer is a pull.
A push or a pull always happens between two things: the one doing it and the one it acts on.
Scientists call a push or a pull a force.

Key idea

Still things stay still

A ball sitting on the grass will not move by itself.
It starts to move only when something pushes or pulls it.
That could be a foot, a hand, the wind or a dog's nose.

Key idea

What a push or pull can do

A push or a pull can start a thing moving.
It can stop a moving thing, like a goalkeeper catching a ball.
It can make a thing go faster or slower.
It can make a thing change direction, like a bat hitting a ball.
It can change a thing's shape, like squashing a ball of play dough.

Four small pictures of a ball: a push starts it moving, a push against it stops it, a push from the side turns it, and pushes from both sides squash it

Key idea

Try it: what did the push or pull do?

Key idea

Bigger push, bigger change

A gentle push makes a ball roll slowly, and only a little way.
A hard push makes it roll fast and far.
A bigger push or pull makes a bigger change in how a thing moves.

Key idea

Pushes can change shape

Squash play dough and it stays flat.
Squeeze a sponge and it springs back when you let go.
Push hard on a brick and nothing seems to change.
What happens depends on what the thing is made of.

Key idea

Rough, smooth, air and water

A toy car rolls a long way on a smooth floor. On carpet it slows down and stops quickly.
Rough surfaces rub more on things moving over them. This rubbing is called friction.
Air and water push back on things that move through them.
A thing's shape matters too. A boat with a pointed front moves through water more easily than a flat box.

Worked example

Example: one car, three surfaces

Room 3 let the same toy car roll down the same ramp onto three surfaces. They did each surface three times, and the results were close each time.
Which surface let the car roll furthest, and why?

Surface	How far it rolled
Wood floor	210 cm
Concrete path	145 cm
Carpet	60 cm

Bar graph of how far a toy car rolled: 210 cm on the wood floor, 145 cm on the concrete path and 60 cm on the carpet

Same car, same ramp, only the surface changeda fair test
Wood floor 210 cm is the longest; carpet 60 cm is the shortest
The smooth wood floor let the car roll furthest. Rough carpet rubbed it most, so it stopped soonest
The three tries were close, so the pattern is real

Key idea

Try it: far or short roll?

Worked example

Example: flat paper or a paper ball?

Two sheets of the same paper are dropped from the same height. One is flat. One is scrunched into a ball.
Which lands first?

Both are the same paper, so only the shape is different
The flat sheet has to push lots of air out of the way, so it floats down slowly
The ball pushes only a little air, so it falls fast
The paper ball lands first, because of its shape

Common mistakes

A rolling ball stops because it runs out of push.
It stops because the ground and the air rub against it; on a smoother surface it rolls further.
We can change the car and the surface at the same time to test the surface.
Change only one thing at a time, or you cannot tell which change made the difference.
A soft push and a hard push do the same thing.
A harder push makes a bigger change, so the ball goes faster and further.

Try it at home

Roll test on different floors

You need: a toy car, a big hardcover book or a flat board, a pile of 3 books, a tape measure, a towel

Lean the big book on the pile of books to make a ramp on a hard floor.
Hold the car at the top of the ramp and let it go. Do not push it.
Measure how far it rolled from the bottom of the ramp. Do it three times.
Lay the towel flat at the bottom of the ramp and do the same three times.
Look for this: the car rolls further on the smooth floor than on the rough towel, every time.

Safety: Set up the ramp where nobody is walking, and put the books away afterwards so nobody trips over them.

Your turn

You open a door by pulling the handle towards you. Is that a push or a pull?

A ball is sitting still on the floor. What will make it start to move?

Ana kicks a ball gently, then kicks it hard. Which kick sends it further?

Where would a marble roll furthest: on sand, on grass, or on a kitchen floor?

You squeeze a sponge and let go. What happens to its shape?

Show answer

1. A pull, because the door comes towards you. 2. A push or a pull. 3. The hard kick, because a bigger push makes a bigger change. 4. The kitchen floor, because it is the smoothest. 5. It springs back to its first shape.

Try it

Forces and Motion: Basics

Full screen · PhET Interactive Simulations, University of Colorado Boulder, CC BY 4.0

Summary

Recap

A push or a pull is a force between two things.
Still things only start moving when they are pushed or pulled.
Pushes and pulls can start, stop, speed up, slow down or turn things, and change their shape.
A bigger push makes a bigger change.
Rough surfaces, air and water slow things down; shape matters too.
In a test, change only one thing at a time.

Maths

The maths behind it

Year 3 MathsMeasuring Length, Mass, Capacity and Area Year 3 MathsBar Graphs and Dot Plots: Reading the Story

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